Find the other endpoint of the line segment with the given endpoint and midpoint. Please help

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

If a is a nonzero real number then the reciprocal of a is

36x2 + 49y2 = 1,764 the foci are located at: (-√13, 0) and (√13,0) (0, -√13) and (0,√13) (-1, 0) and (1, 0)edit: the answer is (- the square root of 13, 0) and (the square root of 13, 0)